Along with the progress in diagnostic or medical technology, various methods for detecting analytes of interest in test samples (such as serum, plasma, whole blood, etc.) have been developed and put into use to enable the early detection of various diseases and for confirming the effects of therapy. For the purpose of qualitative or quantitative detection of an analyte in a test sample, certain detectable compounds (also known as detectable labels or signal generating compounds) are used. Typically, these detectable compounds are capable of being used to generate detectable signals in the presence of one or more analytes in a test sample. In certain instances, these detectable compounds are attached to substances that have a certain affinity for the analyte to be detected and quantified. For example, an antibody can be conjugated to a detectable compound (the labeled antibody is referred to herein as a “conjugate”). The conjugate can then be used to detect and quantify the amount of an antigen of interest in a test sample. In other instances, however, the detectable compound is simply added to the test sample alone, not attached or conjugated to another substance (such as an antibody). Regardless of whether a detectable compound is attached or conjugated to another substance or used alone, once added to the test sample, the compound is activated and the signal detected. As a result, a determination of the presence of an analyte and the amount of the analyte contained in a test sample can be readily determined.
A variety of detectable compounds have been developed and used to generate detectable signals. Such compounds include, but are not limited to, radioactive substances, fluorescent substances, enzymes or metal colloids. In recent years, however, chemiluminescence methods using acridinium derivatives have drawn attention in view of their high sensitivity. Intense luminescence can be generated by reaction of acridinium derivatives with hydrogen peroxide under strong alkaline conditions (See, EP-A 830629 etc.). A number of acridinium derivatives are known in the art and are commercially available. While largely interchangeable, these acridinium derivatives can differ to at least some extent in terms of their physicochemical properties. Such differences can make a particular acridinium derivative either more or less preferred for the detection of an analyte of interest in a sample.
For this reason, there remains a need in the art for acridinium derivatives that can be employed for detecting an analyte in a test sample, as well as methods and kits for using such acridinium derivatives for the qualitative and/or quantitative detection of analyte. The present invention provides among other things such methods and kits.